Forming fabrics used on papermaking machinery are of a great variety, examples of which are single layer and double layer fabrics. In use these fabrics are mounted on the machine in the form of a conveyor or endless belt. When the forming fabric is produced as a flat fabric it must be made endless and into a belt by joining the ends. Many methods are used to seam including the utilization of sewn in loops. It has been generally accepted in the art that for a particular seam to be useful it must not be greater in thickness than the main body of the fabric and the permeability to liquid of the fabric and seam must be substantially the same, otherwise undesirable marking of the paper being formed can occur. These criteria are especially difficult to satisfy in single layer fabrics.
Presently there are a number of papermaking machines and specifically inverform machines where forming fabrics can only be installed by a time consuming hand weaving process. On non-cantilevered inverform machines where the forming fabric must be supplied as an open ended, flat cloth and joined or rewoven into an endless belt on the machine many man hours of work and extended periods of machine down time are required. The standard method utilized for many years for installation of bronze wire forming media was to braze two edges after preparation. This method cannot be used for plastic forming fabrics which must be spliced together by a hand weaving process to form the endless belt. Glues, adhesives and/or welding of the seam area is not satisfactory due to marking of the paper sheet. Non-marking pin seams have been available for two layer woven fabrics but satisfactory pin seams have not been available for single layer fabrics.
All presently used methods of joining plastic fabrics, both single layer and multilayer, into endless belts, apart from hand woven splices, are either mechanically weak or impart an objectionable mark to the paper sheet. The hand woven splice method is excessively time consuming on these high cost production machines.